Method of minimizing adhesion between rubber insulation layers of electric conductors and the resultant article



Oct 1950 J. H. INGMANSON METHOD OF MINIMIZING ADHESION BETWEEN RUBBER INSULATION-LAYERS 0F ELECTRIC CONDUCTORS I AND THE RESULTANT ARTICLE Filed Aprll 26, 1949 wk You wwk wiaw am E &

Patented Oct. 17,1950

METHOD OF MINIMIZING ADHESION BE- TWEEN RUBBERINSULATION LAYERS OF ELECTRIC 'CONDUCTORS AND THE RE- SULTANT ARTICLE John H. Ingmanson, New Haven, Conn., assignor to The Whitney Blake Company, Hamden, Conn., a corporation of Connecticut Application April 26, 1949, Serial No. 89,648

. of multiple conductors, and for other purposes well known in the art Heretofore, it ..h'as'been the practice, in order to minimize adhesion between layers of rubber insulation of the character above referred to, to coat an inner layer with a dust such, for instance, as talc or the like. The use of talc or the like should, theoretically, serve to provide reasonably satisfactory results, but it is an extremely difficult task to apply such dust-like materials in sufficient amount and suificiently uniformly to an inner layer of rubber so as to reliablyminimize the adhesions referred to.

' Furthermore, the use of talc or similar dusty materials to minimize adhesion between layers of rubber occasions so much friction in the extrusion apparatus as to cause frequent breakages of the Wire.

The main object of the present invention is to provide a superior method whereby an electric conductor may be rapidly and economically pro vided with multiple layers of rubber insulation, which latter will not adhere to such a degree as will preclude the convenient stripping of one such layer from another.

A further object of the present invention is to provide a superior method which will produce the results just above referred to and in addition enable an outer sheath of rubber to be applied by means ofan extrusion apparatus without occasioning the frequent breakage of the conductors. 7 Another object of the present invention is to provide a superior electric conductor having multiple layers of insulation and having the outer surface of an inner layer of such insulation of such uniform non-bonding character as will permit the ready separation of an outer layer of insulation therefrom.

With the above and other objects in View, as will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. l is a schematic view mainly in vertical central section and partly in elevation illustrating 6 Claims. (Cl. 18-59) an apparatus suitabl e for carrying out the meth- 0d of the present invention;

Fig. 2 is a perspective view of a fragment of double-conductor" electric wire having two layers of rubber insulation and capable of being produced by the apparatus illustrated in Fig. 1; and

Fig. 3 is 'a perspective view similar to Fig. 2 but showing the facility with which the outer layer of rubber insulation may be stripped from the respective inner layers of the two electric conductors or wires. V

As will be apparent from the following considered in conjunction with the accompanying drawings, the method of the present invention contemplates the application of an outer layer of rubber insulation over an inner layer of rubber insulation which contains an electric conductor, but only after such inner layer has had its outer surface oxidized and subsequently coated with a suitable combined lubricant and antiadhesion liquid which the latter is, by the said ductor which includes two bundles of electric wires respectively designated by the reference characters l0 and -II, which bundles are insulated by being respectively provided with layers or sheaths of rubber insulation [2 and I3. Jointly laterally enveloping both of the inner layers or sheaths l2 and I3 is an outer layer or sheath l4 also formed of suitable rubber insulating material and having a thin but definite web or wall 15 located between the two said layers l2 and I3. In the drawings, the thickness of the web !5 is slightly exaggerated over normal in order to make the illustration clearer.

Normally the task of effectively insulating the bundles of electric wires H] and H is taken care of by the inner layers or sheaths I 2 and I 3 respectively. The outer sheath or layer it is employed mainly as mechanical protection and, in the present instance, to mechanically bind the two inner sheaths l2 and 3 into a unitary plural conductor, though the said outer sheath also is of insulating material.

As before pointed out, it is the main object of the presentinvention to enable the outer layer or sheath I4 to be readily parted from one or more inner layers or sheaths, such as 12 and 13, in the manner indicated in Fig. 3. To effect the separation referred to, it is common practice in the art to provide the said outer layer or sheath [4 with one or more longitudinal slits or cuts l6, indicated inFig. 3, following which the said outer layer may be pulled back to thus lay bare the inner layers or sheaths l2 and I3 and to tear the thin web or wall [5;

To enable the operation illustrated in Fig. 3

to be readily performed, any suitable apparatus may be employed for treating the surfaces of the previously-vulcanized inner layers or sheaths I2 and I3 and for applying the outer layer or sheath I4 thereover. In the accompanying drawings, there is illustrated a tank I! adapted to contain a suitableoxidizing bath such as liquids of the following general nature, for instance:

(a) 2 parts sodium hypochlorite, 1 part hydrochloric acid'and about 200 parts water;

(b) About 0.2% to about 0.6% bromine dispersed in a suitable solvent such as carbon tetrachloride, methylene chloride, carbon disulphide or the like;

' About 0.3% to about 0.8% sulphur chloride (preferably monochloride) dispersed in a suitable solvent such as carbon tetrachloride or the like.

Located over the open upper end of the tank I! are two pulleys I8 and I9 and located adjacent the bottom of the said tank below the liquid level therein is another pulley 20.

The two bundles of electric wires I I] and II with their respective previously-vulcanized rubber sheaths I2 and I3 applied thereover, are led from any suitable reel or other source of supply (not shown) over the pulley I8 and thence downwardly into the tank I! around the pulley 20 and back up over the pulley I9, all as indicated in Fig. 1. The wire is then led horizontally to the left (as viewed in Fig. 1) through an apertured casing 2|, thence through a guide-tube 22 (forming a feature of an extrusion apparatus) and thence outwardly through a tube 23, which may be of any desired length and which may be heated to effect the vulcanization of the outer sheath I4 should such vulcanization be required.

The casing 2| before referred to contains in its interior a mass of felted material 24 such, for instance, as cotton waste, .to which a suitable anti-adhesion and lubricating material may be fed from a tank 25 through a pipe 26 having a control-valve 2'! therein, all as indicated in Fig. l.

The extrusion apparatus of which the guidetube 22 before referred to forms a feature, also includes a body-member 28 in a passage 29 of which the said guide-tube 22 is rigidly mounted. The said passage 29 extends from end to end of the body-member 28 and in addition to holding the guide-tube 22, also holds a die-member 30.

, Above its horizontal passage 29 before referred to, the body-member 28 is formed with a vertical charge-receiving chamber 3| having a contracted. lower portion communicating with the intermediate portion of the passage 29 and hence also in communication with the .passage formed between ing the plastic insulating material out of the lower portion of the charge-receiving chamber 3| and coincidentally onto the exteriors of the inner sheaths I2 and I3 to form the outer sheath I4, there is provided a ram 33, which latter may be forced downwardly, as required, by any suitable means well known in the art.

As will be apparent by reference to the lefthand portion of Fig. 1,- the tube 23 is mounted upon the body-member 28 in axial alignment with the guide-tube 22 and die-member 30, while the unit comprising the casing 2I and elements 24, 25, 26 and 2'! is attached, for convenience, to the end of the body-member 2B opposite the tube 23. It will be further noted that the casing 2I is so positioned as to permit the conductor to pass therethrough and through the :body of felted material 24 without deflecting the conductor out of its normal path.

Both the inner sheaths I 2I3 and the outer sheath I4 may be formed of natural rubber compounds, synthetic rubber compounds, or mixtures thereof and all of which are characterized by having a tendency to adhere to other rubbers against which they are placed especially when hot. Among the synthetic rubbers found suitable may be mentioned butyl rubber compounds and neoprene rubber compounds.

The anti-adhesion material which may be placed in the tank 25 for being fed to the felted material 24 (and thence to the surfaces of the sheaths I2 and I3) may assume a wide variety of forms such. for instance, as glycerine, ethylene glycol, diethylene glycol and triethylene glycol or mixtures thereof either undiluted or diluted with water or any other suitable solvent.

The two bundles of electric wires I9 and II each with its respective vulcanized rubber sheaths I2 and I3 may be drawn from any suitable reel or other source of supply and passed over the pulleys I 8, 20 and I9 and thence through the other features of the apparatus, as indicated in Fig. 1. In Fig. 1, only one of the sheaths, namely, I2, shows in the foreground since the remaining one is in the background.

The pair of sheaths I2 and I3 together with their respective bundles of electric wires II! and II may be drawn through the apparatus by any suitable means common in theart and operating to maintain the strands under tension.

As the sheaths I 2 and I3 pass through the oxidizing liquid contained within the tank I'I, their surfaces will be oxidized to a suflicient degree as they complete their passage through the solution, which oxidized surface is indicated by the fine stippling in Fig. 1. The time of exposure of the sheaths I2 and I3 to the various oxidizing liquids mat vary over a wide range. For instance. the respective times of exposure at room temperatures for the various oxidizing baths (,a) (b) and (0) may be respectively about 15 to 20 seconds, 10 to 20 seconds and 10 to 20 seconds.

After having their surfaces oxidized and dried, the sheaths I2 and I3 will pass through the mass of felted material 24 and will there receive a thin coating of anti-adhesion material from the contents of the tank '25, which material will thoroughly wet and cover the previously-oxidized surfaces, in the manner indicated by the coarse stippling in Fig. l. The anti-adhesion material not only serves to reduce or substantially eliminate the tendency of the outer sheath I4 to stick to the inner sheaths I2 and I3, but also will serve as a lubricant to enable the said sheaths to pass through the guide-tube 22 without such frictional resistance as might cause the breakage of the strands.

As the now-coated sheaths I2 and I3 pass out of the left end of the guide-tube 22, they-will have extruded upon them the outer layer or sheath I4, as is indicated at the left of Fig. 1. This outer layer is then vulcanized.

It will be understood, that in accordance with customary practice in the art, the speed at which the two strands comprising respectively the elements l0--l2 and H-l3 are pulled through the extrusion apparatus, will be synchronized with the downward movement of the ram 33 so as to insure the proper application of the Outersheath or layer l4 over the said strands.

Under some conditions, it is preferred to oxidize the surfaces of the inner sheaths l2 and I3 as a separate operation and to store the same together with their conductors l0 and l I, upon a suitable reel for later being provided with an outer sheath such as [4.

The oxidation of the surfaces of the inner sheaths l2 and i3 as before described after vulcanization and prior to the application of the anti-adhesion liquid, will serve to prevent the appreciable penetration of such liquid into the rubber from which the said inner sheaths are formed, to thus not only guard against the use of an undue amount of anti-adhesion liquid, but also to guard against the deterioration of the said inner sheaths.

Furthermore, the said anti-adhesion liquid thoroughly lubricates the said inner sheaths and thereby relieves them of such frictional restraint as would occasion frequent breakages as the strands are pulled through the extrusion apparatus.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

I claim:

l. The method for minimizing adhesion between layers of rubber insulation on an electric conductor, comprising: passing an insulated wire having a vulcanized rubber insulating-sheath through an oxidizing-bath and thereby oxidizing the outer surface of the rubber insulating-sheath thereof and rendering the said surface suitable for the uniform distribution thereover of the hereinafter-mentioned anti-adhesioh liquid and minimizing the penetration of the latter into the said sheath; subsequently coating the now-oxidized surface of the aforesaid insulating-sheath with an anti-adhesion liquid; and, after the application of the said liquid and while the same is still in place, applying an outer rubber sheath over the first-mentioned rubber insulatingsheath and its said coating, and then vulcanizing said outer rubber sheath.

2. The method for minimizing adhesion between layers of rubber insulation on an electric conductor, comprising: passing an insulated wire having a rubber insulating-sheath through an oxidizing-bath and thereby oxidizing the outer surface of the rubber insulating-sheath thereof and rendering the said surface suitable for the uniform distribution thereover of the hereinaftermentioned anti-adhesion liquid and minimizing the penetration of the latter into the said sheath; subsequently wiping on a coating of anti-adhesion liquid over the now-oxidized surface of the aforesaid insulating-sheath; and, after the application of the said liquid and while the same is still in place, applying an outer rubber sheath over the first-mentioned rubber insulating-sheath and its said coating.

3. The method for minimizing adhesion between layers of rubber insulation on an eiectric conductor, comprising: passing an insulated wire having a rubber insulating-sheath through an oxidizing-bath and thereby oxidizing the outer surface of the rubber insulating-sheath thereof and rendering the said surface suitable for the uniform distribution thereover of the hereinaftermentioned anti-adhesion liquid and minimizing the penetration of the latter into the said sheath; subsequently coating the now-oxidized surface of the aforesaid insulating-sheath with an antiadhesion liquid; and, after the application of the said liquid and while the same is still in place, hot-extruding an outer rubber sheath over the first-mentioned rubber insulating-sheath and its said coating.

4. The method for minimizing adhesion between layers of rubber insulation on an electric conductor, comprising: passing an insulated wire having a vulcanized rubber insulating-sheath through an oxidizing-bath and thereby oxidizing the outer surface of the rubber insulating-sheath thereof and rendering the said surface suitable for the uniform distribution thereover of the hereinafter-mentioned anti-adhesion liquid and minimizing the penetration of the latter into the said sheath; subsequently wiping on a coating of anti-adhesion liquid over the now-oxidized surface of the aforesaid insulating-sheath; and, after the application of the said liquid and while the same is still in place, hot-extruding an outer rubber sheath over the first-mentioned rubber insulating-sheath and its said coating, and then vulcanizing said outer rubber-sheath.

5. An electric conductor having multiple layers of readily-separable rubber and including in combination: an electric conductor; a first insulating-sheath of rubber enveloping the said electric conductor and having an oxidized outer surface; an anti-adhesion liquid covering the said oxidized surface; and a second sheath of rubber enveloping the said first insulating-sheath of rubber and the said anti-adhesion coating thereon.

6. A plural electric conductor having multiple conductors and multiple layers of readily-separable rubber and including in combination: a plurality of electric conductors; a plurality of inner insulating-sheaths of vulcanized rubber respectively enveloping the said electric conductors and each having an oxidized outer surface; an anti-adhesion liquid covering the said oxidized surfaces; and an outer sheath of vulcanized rubber jointly enveloping the said inner insulatingsheaths of rubber and the respective anti-adhesion coatings thereon.

JOHN H. INGMANSON.

REFERENCES CITED The following references are of record in the file of this patent: 

